1. Field
The invention relates to methods and apparatuses for applying metallic coating layers over cores of metallic rods and wires.
2. Related Art and Background
For many practical applications, such as power transmission, it is desirable to produce wires including a core of copper, or copper based alloy, coated by an aluminum cladding layer. There are several conventional methods in use for applying an aluminum cladding to a copper core for various applications.
A first method, described in U.S. Pat. No. 2,947,069, requires the application of an intermediate cladding of another metal such as silver to a copper rod by means of spraying, electroplating or wrapping with foil. The silver clad rod is then inserted into a sleeve or tube of aluminum alloy and the whole is then subjected to a cross section reduction of 30% to 40%. The resultant rod is then annealed to help improve the metallurgical bond between the three metals. Further, the cross section of the rod is reduced by drawing to the desired wire diameter. Problems with this method include the fact that the initial length of the rod is limited to about 25 feet. This, severely limits the length of the final product available. Moreover, the high cost of the silver component further inhibits the widespread use of this method.
Another method for applying an aluminum cladding to a copper core is described in U.S. Pat. Pub. No. 2007/0221706. In this method, aluminum cladding is applied to a copper wire by applying one or two strips of aluminum to the surface of the copper wire and compressing the strip and wire together at high pressure in a process such as roll-forming. One of the drawbacks for this procedure is that it involves elaborate surface cleaning and preparation which must be carried out on both the copper wire and the aluminum strip prior to the cladding process. This preparation and cleaning procedures involves heat treatment in both oxidizing and reducing atmospheres.
The methods and apparatuses in this application overcome some of the drawbacks and shortcomings of the conventional procedures for forming metallic aluminum coating layers over cores of metallic copper rods and wires.
The above information disclosed in this background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any part of the prior art.